Gear-truing machine.



DE WI'IT G. OOOKINGHAM & J. H. HERTNER.

GEAR TRUING MACHINE. APPLICATION FILED NOV. 30, 1910.

Patented Apr. 8, 1913. I

4 SHEETS-SHEET 1.

DE WITT U. COOKINGHAM & J. H. HERTNER.

GEAR TRUING MACHINE. APPLICATION FILED NOV. 30, 1910.

1,058,353. Patented Apr. 8, 1913.

4 sums-5112M 2.

GEAR TRUING MACHINE. APPLICATION FILED NOV. 30, 1910.

Patented Apr. 8, 1913.

4 SHEETS-SHEET 3.

FAQ.

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GEAR TRUING MACHINE. Y APPLIOATION FILED NOV. 39, 1910.

1,058,353. Patented Apr. 8, 1913.

4 SHEETSSHELET 4.

ZZZW 13 #6. 9 AWTORN v i 2 severe usage to which the gears just named UNITED STATES. PATENT OFFICE.

TO THE MUCH AND LANG CARRIAGE PORATION' OF OHIO.

' GEAR-Tamils MACHINE.

' DE WITT c. oooxmennm AND JOHN H. HEB'INEB, 0F CLEVELAND, onro, VASSIGNORS QOMPANY, OF CLEVELAND, OHIO, A' COR- Pat-entai 8,1913.

Application filed November 30, 1910. Serial .No. 594,982,

To all whom it may concern:

Be it known that we, DE W'I'r'r 0. (100K- I'NGHAM and JOHN HnHERTNER, citizens of the United States, and residents of Cleveland, county of Cuyahoga, State of-Ohio, have jointly invented a new and'useful'Improvement in Gear-Truing Machines, of which the following is a specification, the principle of the invention being herein explained and the best mode in which we 1 have contemplated applying that principle, so as to distinguish it from other inventions.

Among the refinement-s which have been introduced into various manufacturing processes and operations by the expansion and perfection of the. automobile industry, may be included the trimming and truing of. gears for use in connection with automobilesand more particularly with the driving mechanism of automobiles.- Owing to the are subjected, it has become necessary to temper or harden them, which of course, is

only feasible after they have been out. As. a result, however, of .such hardening, the gears are apt .to be warped more or less,

I which is objectionable, since even where the warpage or distortion, is veryslight, the op- I eration of the. gear will berendered noisy if;

not actually ineflic-ient. It has accordingly become the practice to grind the teeth of,

such gears after the hardening or tempering process, in order to render them exactly true and insure their perfect meshing, when assembled in'the completed mechanism.

Our present invention, then, has as its objectthe provision of efiicient means fori thus truing ars by grinding theinteeth to;

conform per ectly to the designupon whichj they have been laid out and cut. I

, 'More'especially the present improvements are concerned with means for thus trimming or truing beveled gears, which, so far as we are aware, have never heretofore been successfully' trimmed 'or ground on a commercial scale, 'owing to certain obvious difliculties compared with the truing of ordinary spur gears. .In this latter operation, a formed rinding disk can be used, so that, by mere y preserving the contour of such.

disk, perfectly ground teeth on the gear can be assured. This, however, is not possible in the case of beveled gear teeth, while to use the edge of the grinding disk or wheel, as alone is possible inmachines previously designed forthe purpose .in hand, is impracticable owing to the importance of reserving such edge. With a view, then, to

the accomplishment of the above named and related objects, the present invention consists of the means hereinafter fully described and particularly pointed out in the claims.

The annexed drawings and the following description set forth in detail certain mechanism embodying the invention, such dis-j closed means constituting, however, but several of the various mechanical forms in whichthe principle of. the invent-ion may be use J I In saidannexed drawings :-.'Figure 1 is a perspective. view of a gear truing machine embodying our present improvements; Fig.

2 is a plan view of the essential parts of such machine; Fig. 3 is a side elevational view of the same; Fig. 4 is a sectional view of the shaft used to support the gear during the truing and trimming operation together withcert-ain associated parts, the plane of the section'beingfindicated by the line 4-4, Fig. 2; Fig. 5 is an end' elevation of such shaft and parts; Fig. 6 is a diagrammatic view illustrating the method exemplified in the operation of. the machine; Fig. 7 is 'a .plan view corresponding to Fig.2, but illustrating certain modifications in the constructi'on of the machine; Fig. 8 is a side elevational view of such modified construction, it being notedcthat both in Figs. 3 and 8. the gear being operated upon is shown in sect-ion; and Fig. 9 is a side elevation of yet another modification.

The. general features of the machine need .be but briefly noted, inasmuch as they do- -notdifier from familiar types of grinding .inachine's. Thus a table 1 is provided, shiftable: in right-angularly related horizontal directions beneath a grindin tably supported in a vertica plane alined with onesuch direction. The driving conmotions for the spindle that carries ,the

grinding disk, as well as the feed mechanism disk' 2 rotafor'shifting the table in the two directions I just referred to, need notbediscribed in detail, as they are all well-known construct-ions. Upon the table is supported the base 3 of the mechanism'of present interest, it

being upon this base that the gear 4: to be a ground is supported.

Referring more particularly to Figs. 2 and i i 3, it will be seen that a standard 5 is pro: vided at one end of such base, preferably of the recurved form illustrated, so as'to 40 trimming or extend inwardly over the base While still leaving a clear space for the movement of certain parts, as Will be hereinafter more fully described. This standard is provided with a socket-bearing 6 composed of plates secured thereto and to each other, such plates having their contiguous faces formed. with spherical concavit-ies (shown in Fig. 4:) adapted to receive the spherical, or ball-like, terminal 7 of the work-supportingspindle or shaft 8. The construction of the latter is preferably made as light as possible consistent with a proper degree of rigidit inasmuch as its weight, in the simpler fbrm of machine at least, will be sustained by the operator, when the machine is' in use.

Accordin ly said spindle is made of a section 0 pipe, or other tubular material, save for a short section at its inner end Where a solid shaft 9 .is provided to receive the gear to be operated upon. Such section 9 is provided with a key-way 10, so that the gear is non-rotatably held thereon, while at the same time it is clamped between the end of the tubular portion of the shaft and a threaded collar 11, so as to be held securely against lon 'tudinal movement a on the shaft. According y, in order to take to be parallel with that direction of the movement of the base 3, With which the plane of the grinding disk is alined. At the" opposite end of the base, from that bearing the standard 5, there extends a finderarm 12 provided at its outer extremity with a lateral fprojection 13 of an lar outline, one

. edge o such rejection lying in a prolongation' of the ine ar -w, previously referred 1 to as passing through the center of the shafts pivotal attachment to the standard 5, and the cutting edge of the disk 2, and

the face of such projection lying in the same plane as one of the lateral faces of the grindmg disk.

B supporting at the outer. end of the' sha t at a proper radial distance from said shafts axis, a templet of the same cross-sectional form as a tooth of. the gear to be trued and of a size to correspond with the distance of such tem late from the point of ivotal attachment ofbaidshaft as compare with the distance of the ear 4 being ground from i such point, it wilhbe seen ,that upon manipulating the shaft so as to bring any point on the lateral thedisk 2 used in the grlnding operation, is designedthe plane surface of such enlar ed tooth into contact with the edge of the nder just referred to, a corresponding point on the alined tooth of the gear will be presented to face of the grinder. .Hence, if such gear tooth be not perfect, the grinding will obviously penetrate its surface until such surface is rendered perfectly true., By

bringing successive points on the guiding tooth into contact with the finder, the grinding disk will be caused to true corresponding points on the gear, so that by a proper reciprocation of the base 3 efi'ected through the feeding movement of the table upon which it is mounted, the entire surface of the particular tooth corresponding in position with the guide tooth may bet-rimmed oil, or ground, to the proper contour. In

other words the relation of the several parts of the machine will be rendered clear by 35 considering the operative lateral face of the diskand the face of the finder as lying in the same plane, which plane is intersected by the line which defines the axis of the shaft. The gear tooth and templet then being carried on said shaft so as to bear a similar relation to such axial line, the cross- .sectional form 'of said gear tooth and tem- 'plet being the same, and their relative size proportionate to their distance from the point of intersection of the line with the' plane, it will be seen that corresponding points on both will simultaneously be brought into tangency with such plane by proper mani ulation of the shaft. The contact is in e ect a surface contact, it bein against the sides of the grinding disk and the finder that the gear tooth and templet are V respectively pressed. The relation of the gear to the guide tooth and of the latter to the finder, the face of which it will be re 'membered is in line with the operative face of. the grinding disk, isshown 1n end-wise elevation in-Fig. 6; from this figure, taken in conjunction with Figs. 1 and 3, the manner in which the several parts cooperate in the operation just described should be readily grasped.

The guide tooth or templet 14, as it may properly be termed, is sup orted at the outer end of an arm 15 rotata 1y mounted upon the free end of the shaft 8, being clamped against certain other parts bymeans of a nut 16 that is in turn secured against rota tion, once the parts are positioned, by a second or lock nut 17. Sad templet tooth is not onl thus supported at a proper radial I distance om the axis of the shaft to correspond with its distance from the point of plvotal attachment of the shaft to the sup- 12F porting standard 5, but also at an angle corresponding with the bevel of the gear which is being trimmed.

The parts against which the supporting arm 15 for the tooth is clamped upon the 130.

end of the shaft comprise firstof, all a disk 18 that is non-rotatably secured to the shaft andprovided near its edge with a circular series of engaging elements in the form of apertures 19 equidistantly spaced about the circumferenceofthe diskand corresponding in number to the number of teeth on the particular gear 4 which it is desired to trim, or true. Between such disk and the tooth-supporting arm 15, is a second arm 20 similarly rotatably mounted upon the shaft and adapted to be clamped thereagainst, along with the disk and said tooth-supporting arm. In the outer end of this second arm is a resiliently mounted plunger 21, the inner end of which is adapted to engage with any selected one of the-apertures 19 in thedisk 18. The two arms and are- 'adjustably connected together by means of a segmental, slotted guide 22 carried by such firstarm (see Fig. 5) and extending over the second arm and clamped thereto by means of a'clamp-nut 23 threaded upon a d stud carried by such secondarm. In order tance between the two arms, a bolt 24. piv-- 1 bring to adjust quite accurately, the angular disotally secured to the first arm is loosely passed through a bifurcated lug in the second arm and has threaded upon ita knurled'nut 26, which is held between theportions in such lug and so adapted, upon being rotated, to move the bolt in one di-' rection or the other.

' The solid outer end of the shaft which 1' several parts-just described is.

receives the preferably rounded off to form a handle 27, v

as shown in the several figures, so that the operator grasping swing the shaft the same, may readily aboutthe point of its pivotal 1 attachment to the standard 5, in order to guide tooth ortemplet 14 intolcontactwith l the edge of'the projection l3on'the finder 12'.

- The generaloperatipn of the form of ma- T chine just described may now be. readily followed-z- The beveled 'gea 7 subsequently .utilized'in securing such gear,-

' some difiiculty,"

Lto' be 'all points along the outline of the trimmed or trued is first securely clam ed in] place upon theinnenend the latter then secured in the socket-bearing providedtherefo The key+way in suchgear'wher'ewithf'key 10 engages, it,-,wil l'.be understood, isthe same key-way whiehi" is in the mechanism, of which it ,is ultimately totform a part. -.As itwill be a matter of or at least trouble, to make I the angularjposition of this key-way with respect to 7 same in a sfirles of-gears,

be adjacent teeth; always the the adjusta is indexing means for locating the templetor guide:tooth 11-14; atthef outer I end' -of the shaft- Aceordingly,-

one of the apertures 19 in the indexplate;

- of the slut t and.

we have provided.-

1 the; next I step in thevv operat on j is t] secure the- "arm I QO'wi th the p] ungerillz carried thereby ilr'ahye plunger in .defined by the guide that is oscillatorily mountedupon the ,disk' is thus initial pos t on, of a gage co'nsi the-rfir'st arm carrying the trimming of -i-course swung a w ry e; a m o the; diamondi-i carrying arm28-is turned forwardly into. operative.

Whenever' the more particularly,

18, such apertures corresponding approximately with the location of the teeth on the gear. The arm 15 which carries the templet is then adjusted by means of nut 25, so that when it contacts with the finder, the grinding disk will remove just the proper amount of material from the tooth: without having to cut in too deeply, The amount of material that may be removed is of course,

gaged in the original cutting of the gear, previously to its being hardened or tempered. When this adjustment has been accurately determined the two arms 15 and 20 are securely clamped together by means of the nuts 16 and 17, and for the remaining teeth it is merely necessary to shift the the end of arm 20 from one aperture 19 in theindex plate to the next. By

proper manipulation of the handled shaft each too'this then ground to the true form tooth or templet, the table which carries the support being of course reciprocated the while.

In order to preserve the cutting edge of the disk2 perfect-lytrue, a truing device is provided preferably consisting of a diamond arm 30, similarly oscillatorily; mountedupon the standard mend, 1 Upon swinging this arm forward, the "gage carried thereby i s brought opposite the face of thee-grinding disk and any change in the relative-1 position of the latter may thus be readilydeter-mined. [whens the mathe outer end.of a. second i 11.95 5 and aboutthe same 3X13 8.S-

chine is in operat on; bothqthesef arms are position, it'may be securely :there clamped lock nut" 31 upon the .bolt

means of a which 1 forms the pivotal f axis of Sl1Gl1 jaI'mS.

satires-11mm It, '.wil'l be observed that in-the figures thus far referred to, as 'showingour improved geaz *truing machine, "p e i g i the gear therein apsmall diameter and a small. gear 1or-pins apparatus in que 's gof relatively the grinding of Siuch' arrangement of} h a lge l es ib be'tr'immem-one in-wh h, .1n other admirably adapted. Where,how o'f larg'er diameter re words, the inclination of the teeth to the" axis of the gear more nearly approaches a right angle, it will be evident that to have i .the shaft of any length whatever, would nemodification,

cessitate providing for I of its 'outer end entirely out of the question if-tlre machine is' to be made of practicable dimensions.- Accordingly where gears. of larger radius, having teeth corresponding more; sharply inclined to the gear aixs, are to be'trued, we modify the arrangement of the shaft, as shown in Figs. 7. and 8. This spection of the figures just referred to, con sists' simply in the shortening of the shaft 8, both bylessening the distance between the point of its pivotal attachment to the stand- ,ard and the point at which the layer gear .132 is clamped thereon; as

dex plate 18 which carries the-templet or guide teeth 14. The latter is mounted on an arm 33, that although adjustably secured to the index plate in the same manner as before, is considerably longer, such arm fur- "therinore in this case being madeof. ribbed construction, as that it tooth with sufiicient rigidity. Said tooth, owing to the change in the disposition of'the The shaft in this construction, it will be angles to the outer end appears inFig. 7, in order may serve tosupport such guide axis of the shaft that carries the gear being trimmed, is attachedat substantially right of the arm 33, so as topreserve a" proper successive teeth on the gear as such arm is gradually moved around theindex plate.

' seen, depends downwardly insteadof extending horizontaly from the socket-bearmg 6, in which" its inner ball-shaped end is held; the plates forming such bearing require, accordingly to be 1 difierently. fashioned from those used in connection with the preceding formof apparatus and it is for this reason that these plates are made detachable, namely in order that they can be readily changed to adapt the machine for connected between the handling of difi'erent sizes of gears.

The mode of operation of this modified form the machine is obviously the same as that.

the preceding form, quirespecial attention.

While in both forms of the machinehereinbefore described, it is contemplated that the operator will be able to swing the shaft 8 that carries the gear and. the index plate, Without the burden becoming wearisome, the

and so does not reweight of such parts may be partly or entlrely sustained, and corresponding relief afforded the operator. For this purpose the simplest arrangement is that illustrated in Fig. 9, where theiform'of machine first described, is-shown with a tension spring 34 the outer end of the shaft .8, at apoint just short of the index plate,

The effect of this a range of movement stood that the as will be obvious from an in-;.

moreover, the relative disposition 7 also by lessening the distance between such gear and the in,-

alinement with the point ont-he finder arm. spring isto tend to draw the shaft toward the arm and thus to hold the templet against the edge of the finder, so that all that is required of the operator is to control the movement of such templet along the finders edge. Itwill be underpoint of attachment-of the spring at either end may be varied from that shown, as also that in place of a spring, a counterweight-or like means can be utilized to partially or entirely carry the weight of the shaft and the parts attached thereto. In such two typicalforms of our invention, of the parts, carried by spindle 8 has been the same; in other words, the work, or gear to be ground, is located on said spindle intermediate between the pivot point of the latter in its, bearing and the templet-carrying disk 18. Asa matter'of fact, this disposition may be varied without departing from the spirit of invention; for example, the spindle, by being prolonged through the aforesaid pivot point, may be adapted to carry the work on its inner end without any change in the relative size of the templet. This is also illustrated in Fig. 9, where the spindle 8 is shown as supported by a universal joint 35, beyond which itprojects to receive the gear 34. The latter is reversed in its ,position, and the disk located below the line 00-20, butotherwise no change is involved.

The templet may also, if desired be carried on the spindle between'the latters point of. pivotal support and the work, but as this wouldin'volve the use of a templet smaller, instead of larger, than the tooth being trimmed, such arrangement would not have much practical value in the field of use specified. I

Other modes of applying the principle of our invention may be employed instead of the one explained, change being made as regards'the mechanism'herein disclosed, provided the means stated by any of the following claims or the equivalent of such stated means be employed. We therefore" particularly point out and distinctly claim asour invention 1 1. In mechanism for truing bevel gears, the'combination of a work-holding member having a universal pivotal support; a templet carried by said member and of the same cross-sectional form as a tooth of the gear to be trued; a finder adapted to have a surface contact With said templet; and grinding means adapted to operate upon such. work. 1 2; In mechanism for truing bevel gears, the combination of a relatively reciprocable base and a grinding wheel, the latter being mounted adjacent to the former; a spindle universally pivotally base; a templet carried by said spindle at a.

and a convenient supported upon said of the work, said templet being of the same cross-sectional form as. a tooth of the gear to be trued; and a finder mounted upon said base and adapted. to have a surface contact with said templet.

3. In mechanism for truing bevel gears; the combination of a work-holding member having a universal pivotal support at one end; a templet. carried by said member, said templet being of the same cross-sectional form as a tooth of the gear to be trued, and

the work being secured to. said member at a point intermediate between its pivotally supported end and said templet; a finder adapted to. have a surface contact with said templet; and grinding means adapted to operate upon such work.

4. In mechanism for truing bevel gears, the combination of a relatively reciprocable base and a grinding wheel, the latter being mountedadjacent to the former; a spindle having a"universal pivotal support at one end upon said base; a templet carried by said spindle, said templet being of the same cross-sectional form as a tooth of the gear to be trued,the work being securedto said spindle at a point intermediate between the latters pointof support upon said base, and said templet; and a finder mounted upon said base and adapted to have a surface contact with said templet.

5. In a machine for truing bevel gears, the combination of a suitable base; a grindmg wheel mounted adjacent to said baseand lying in a plane alined with its direction of movement; a spindle detachably secured at one end to said base by a universal pivotal joint; a templet carried by said spindle andhaving the same cross-sectional form as a tooth of the gear to be trued; means for removably securing the gear to be truedupon said spindle at a point intermediatebetween such pivotal joint-and said templet; and a the combinationfof a suitable finder-mounted upon said base and adapted to have a surface contact with saidtemplet.

6. In a machine for truing bevel gears, the combination of a suitable base; a grinding wheel. mounted adjacent to said base;

a-spindle detachably secured at one end to said base by a universal pivotal joint; means for removably securing the gear to be trued upon said'spindle at a point intermediate between the latters ends; a templet having the same cross sectional form as a tooth of such gear, carried upon said spindle. beyondsuch gear; means for securing said templet in positions alined withsuccessive teeth 'on the gear; and afinder mounted upon said base and adapted to have a surface contact with said templet, 7. In a 'machinemfor 'truingJ bevel'gears,

ase; a grinding wheel mounted adjacent to said base;

[6 a spindle detachably' secured at one'end to.

spindle at a, point beyond said gear; means] for securing said templet in position alined with successive teeth on the gear; and a finder mounted upon said base and adaptedto have a surface contact with said; templet..

8. In a machine for truing bevel gears, the combination of a suitable base; a grinding wheel mounted adjacent to" said base; a spindle detachably secured at; one end to saidbase by a universal pivotal joint; means for removably securing the ear to be trued upon said spindle at ap'oint intermediate between the latters ends; a disk non-rotatably mounted upon said spindle beyond such gear and bearing a circular series of engaging elements corresponding in number and posi{ tion with the gear teeth; an arm rotatable about said spindle and adapted; to engage with successive elements on said disk; a templet, having the same cross-sectional form as a tooth of such gear attached to said arm; and a finder mounted upon said bas and adapted to have a surface contact with said templet.

9. In a machine for truin the combination of'a suitablei ing wheel mounted adjacentflto said base;

bevel I gears,

a spindle detachably secured at one end to said base by a' universal pivotal joint; means for removably securing the gear to be trued ase; a grindupon said spindle at a point intermediate 7 between the latters ends; a disk non-rotatably mounted upon said. spindle beyond."

such-gear and bearing a circular series; of engaging elements corresponding 1n number and posit-ion with'the gear teeth; an arm ing wheel mounted adjacent to said "base;

a spindle detachably secured at one end to said base-by a universal pivotal joint; means for removably securing-the gear to be trued upon said spindle at a point intermediate between the latters ends;-ja disk non-rotor;

tably mounted upon said spindle beyond such ar and bearingaicireu lar series of engagin elements corresponding in number and position with the gear teeth; an arm;

rotatable about said spindle and adapted to engage with successive'elements on'said diskyanother arm similarly rotatable. about said spindle adi s a l HiiitS j o n c ing i with a handle; a-

ably clamping the gear to be trued upon said spindle near its a teeth on the gear;

. spindle detachably 'mounted u on said base and adapted to have. a sur ace contact with said templet. 11.

In ,a machine for truing bevel gears,

the combination of a reciprocable base pro- 10" vided with a standard at one end; a grinding wheelmounted adjacent to said base and alined withits direction of movement; a

secured at one end to said standard-by a universal other end of said spindle being provided threaded collar for removpivoted end; a templetcarried upon said spindle near'its handled end;

said templet being of the tional -.lform vas tooth of" the gear to be same CI'OSS-SQC- trued, and a finder mounted at the other end of said'base from said standard and adapted to have a surface contact with said templet. 1

12. lln a machine for truing bevel gears, the combination of a reciprocable base provided with a standard at one end; a grinding wheel mounted adjacent to said base and alined with its direction of movement;

,a spindle detachably secured at one end to said standard by a universal pivotal joint, the other end of said spindle being provided ,with a.handle-;"a' threaded collar for removupon ably clamp ng the gear to be trued 1 said spindle near its pivoted end; a templet,

.tooth of said gear,

having the same cross-sectional form as a carried upon said spindle near its handled end means for securing said templet in positions alined with successive v and a 'finder'mounted at the other end of said base from said stand- I and and adapted to have a surface contact ,wi ha a d i j ably clamping the gear L with said templet.

.-;the combination of vided. with a standard at one end; ing wheel mounted adjacent to said alined with itsdirection of movement; a

spindle detacha-b '13. In a machine for truing bevel gears,

a reciprocable base proa grindbase and ly secured at one end to said-standard by theother end of said spindle being provided threaded collar for removto be trued upon said spindle near its pivoted end; a disk nonrotatably mountedupon-said spindle near its ,handledend-an'd' bearing a circular series of engaging elements corresponding in numher and position with the gear teeth; an

spindle and adaptarmrotatable about said 'ed to engage withsuccessive elements on said disk; a templet, having the same crosssectional form as a tooth of such gear, at]

pivotal joint, the

a universal pivotal joint,

tached .to said arm; and a finder mounted at the other end of said base from said standard and adaptedto have a surface contact with said templet.

14. In a machine for t-ruing bevel gears, the combination of a reciprocable base provided with a standard at one end; a grinding wheel mounted adjacent to said base and alined with its direction of movement; a spindle detachably secured at one end to said standard by a universal pivotal joint, the other end of said'spindle being provided with a handle; a threaded ollar for removably clamping the gear to be trued upon said spindle near its pivoted end; a disk non-rotatably mounted upon said spindle near its handled end and bearing a circular series of engaging elementscorresponding in number and position with the gear teeth;

an arm rotatable about said spindle and adapted to engage with successive elements on said disk; a templet, having the same cross-sectional form as a tooth of such gear, adjustably attached to said arm; and a finder mounted at the other end of said base from said standard and adapted to have a surface contact with saidtemplet.

15. In a machine for truing bevel gears, the combination of a reciprocable base provided with a standard at one end; a grindingwheel mounted adjacent to said base and alined with its direction of movement; a spindle detachably secured at one end to said standard by a universal pivotal joint, the other end of said spindle being provided with a handle; a threaded collar for removably clamping the gear to be trued upon said spindle near its pivoted end; a disk non-rotatably mounted upon said spindle near its handled end and bearing a circular series of apertures corresponding in number and position with the gear teeth; an arm rotatable about said spindle and provided with a plunger adapted to engage successive apertures in said disk; another arm similarly rotatable about said spindle; means adapted to clamp saidarms and disk together; adjustable means connecting said two arms, whereby the last-named arm may be secured in desired angular relation to the first; a templet, corresponding in form witha tooth of such gear, attached to said last-named arm; and a finder mounted at the other end of said base from said standard and adapted to coeperate with said templet.

Signed by usthis 26th day of November, 1910. I a

' 'DEWITT o. OOOKINGHAM.

JOHN H. HERTNER,

Attestd lay- ANNA L. GILL, Jim. T.- OBERLIN. 

